Electrical condenser



May 28, 1957 H. M. WADSWORTH ELECTRICAL CONDENSER Original Filed Jan. 26, 1953 INVENTOR.

fiZiZ/Zdgwvrf/z AT; DRIVE Y United States Patent ELECTRICAL CONDENSER Howard M. Wadsworth, Liverpool, N. Y.

Original application January 26, 1953, Serial No. 333,035,

now Patent No. 2,744,221, dated May 1, 1956. Diviled and this application February 24, 1956, Serial No. 7,530

3 Claims. (Cl. 317-249) The present invention relates to an electrical condenser and more particularly to a trimmer condenser for high frequency oscillating electrical circuits. This is a division of applicants prior application Serial No. 333,035, filed January 26, 1953, now Patent No. 2,744,221.

Electrical condensers of the above type are now commonly constructed by metallizing the exterior of a small dielectric tube to form one plate of the condenser, while a cylindrical metal slug is movably mounted in the interior of the tube to form the other condenser plate.

The dielectric tubes, which are usually made of glass, are subject to significant deviations from true cylindricity, and the traversing means for the inner electrode are often considerably out of line with the axis of the tube. This makes it diflicult to produce an inner electrode having full surface contact with the interior of the tube which will not be liable to break the tube when the electrode is adjusted axially.

It is an object of the present invention to provide a novel trimmer condenser of the above type having an inner electrode formed of sheet metal which is radially pressed outward into substantially full surface contact with the inner surface of the dielectric tube.

It is another object to provide such a trimmer in which the inner electrode is traversed longitudinally with little or no rotary movement within the dielectric tube.

It is another object to provide such a trimmer in which the traversing means for the inner electrode is so constructed as to yieldingly permit some lateral movement of said electrode to accommodate for misalignment in the tube.

It is another object to provide such a trimmer which is free from microphonics such as might be caused by loosely sliding contacts.

It is another object to provide such a trimmer in which the expansive force of the inner electrode may be readily adjusted.

It is another object to provide such a device in which the inner electrode is so formed as to slide smoothly in the tube without any tendency to jam in constrictions or deformations of the tube.

It is another object to provide such a device which is economical to manufacture and assemble, easy to adjust, and which maintains its adjustment securely in spite of vibration or shock.

Further objects and advantages will be apparent from the following description taken in connection with the accompanying drawing, in which:

Fig. l is a side elevation of a trimmer condenser embodying a preferred form of the invention partly broken away and in section;

Fig. 2 is an end view of the same;

Fig. 3 is an enlarged detail in perspective showing the inner electrode of Fig. 1 with the end compression discs removed;

Fig. 4 is an enlarged detail of an inner electrode in section similar to that shown in Fig. 1, with a modified form of end compression discs; and

Fig. 5 is a detail in perspective of one of the compression discs shown in Fig. 4.

In Fig. l of the drawing there is illustrated a trimmer condenser comprising an outer electrode 1 which is in the form of a metallized coating of a dielectric tube 2 of suitable material, such as glass. The electrode 1 is provided with a soldered lead 3 for convenient connection with its intended circuit.

An inner electrode 18 is slidably mounted within the dielectric tube 2 for movement into and out of telescopic relation with the outer electrode 1.

Means for adjusting the inner electrode longitudinally in the tube 2 are provided comprising a shaft 16 which is threaded for at least a portion of its length and traverses a nut 7 rigidly connected to the end of the tube 2 as by means of metallizing and soldering as indicated at 8. The nut 7 is formed with a shoulder 9 and is externally threaded as shown at 11 for the reception of a clamping ring 12 by which the nut 7 may be rigidly mounted in a panel 13.

In the form of the invention illustrated in Figs. 1 to 3, the adjusting shaft 16 is threaded throughout its length, and a sleeve or core 17 of elastically deformable material such as rubber having a normal diameter slightly less than the interior of the tube 2 is mounted adjacent the inner end of said shaft. The inner electrode 18 is shown in the form of a band of sheet metal wrapped around the core 17 with the ends of the band bent inward as shown at 19 and 21 in Fig. 3 to enter loosely into a longitudinal slot 22 formed in the core.

Means are provided for causing the inner electrode to move longitudinally with the shaft 16, and also to expand the inner electrode into full contact with the interior of the tube. As shown in Fig. 1, this is accomplished by means of nuts 23, 24 threaded on the shaft 16 at each end of the electrode and tightened up to compress the core 17 sufficiently to secure the desired expansive pressure for the electrode 18. The nuts 23, 24 are preferably provided with saw-tooth shaped dentals on their sides which are arranged to penetrate the core 17 and prevent the nuts from loosening. The electrical connection between the electrode and shaft 16 may be secured by bending down a tab 25 to make contact with one of the nuts or in any other suitable manner.

In Fig. 4 the inner electrode 18 is the same as illustrated in Fig. 1, but the expanding means is in the form of a pair of annular discs 26, 27 having inwardly extending elastic tongues 28, 29 having slanting engagement with the surface of the shaft 16 to hold the discs compressed against the elastic core 17. In this case, the end of the shaft carrying the electrode may if desired be provided with annular grooves 31 instead of threads.

In both the embodiments of the invention illustrated, the capacity of the trimmer is adjusted by rotation of the shaft 16 in any suitable manner, the nut 7 remaining stationary whereby the overlapping relation of the inner and outer electrodes is varied to secure the desired capacity. When so adjusted, the elastic pressure of the inner electrode against the inner wall of the dielectric tube maintains the adjustment securely.

It will be understood that lateral movement of the shaft with respect to the inner electrode necessary to compensate for misalignment is permitted by the elasticity of the core 17.

Although certain embodiments have been shown and described in detail it will be understood that changes may be made in the precise form and arrangement of the parts illustrated without departing from the spirit of the invention.

What is claimed is:

1.'In a trimmer for high frequency oscillating electrical circuits a stationary cylindrical dielectric tube, an outer electrode. fixedly mounted thereon, an inner electrode comprising a split hollow cylinder, and means for longitudinally adjusting the inner electrode, said ad justing means including means to expand the inner electrode outwardly into substantially full surface contact with the interior of the tube, said adjusting means for the inner electrode comprising a longitudinally adjustable shaft, a core of elastically deformable material fixedly mounted thereon and non-rotatably supporting said electrode on the shaft, and means on the shaft for axially compressing the elastic core.

2. A trimmer condenser as set forth in claim 1 in which aysamo.

4 the means for compressing said elastic core comprises a pair of discs adjustably mounted on the shaft.

3. A trimmer condenser as set forth in claim 2 in which the elastic core is provided with a longitudinally extending slot, and the inner electrode is in the form of a sheet metal hand rolled: around the core with its ends received in said slot.

References Cited in the file of this patent UNITED STATES PATENTS 2,318,415 Patzschke May 4, 1943 2,693,557 Kodama Nov. 2, 1954 FOREIGN PATENTS 628,499 Germany Apr. 6, 1936 

